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79
3. A list of Key AOI entries: A list of two or more Key AOI entries2 this is analogous to
specifying key frames in key frame animation. For each Key AOI entry, the required elements are:
a. Bounding Box: The bounding box of the AOI BBOX=minx, miny, maxx, maxy. The
bounding box values are set in the coordinate reference system set in CRS.
b. Time of acquisition: The time of acquisition TOA of a specific frame within the
collection. This value is specified as a single time value or frame number Time=ISO8601 Time Value; Time=Fnumber. The specified bounding box must
at least partially intersect the bounds of the WAMI frame at that specific instant in time. If the TOA is set as an ISO8601 time value and the captured frame does not fall exactly
at that that time, the server maps it to the closest valid captured frame.
c. ΔT: The time increment. This value is specified as frames or seconds between this key
AOI and the next key AOI. The last key AOI shall have a ΔT of zero. If a client sets a key AOI ΔT to be zero and this key AOI entry is not the last key AOI entry, it means the
client is requesting the server to determine the number of intermediate AOIs to generate. Δ
T is assumed to be in frames if Time of acquisition is set in frames. ΔT is assumed to be in seconds if Time of acquisition is set as an ISO8601 time value.
d. Server-side automation of intermediate frames is useful for sensors whose acquisition frame rate is not constant. For instance, assume that this collection was acquired at the
rate of about 1.8 frames per second: e. Consider that a request comprises of two key AOIs.
f. First key AOI is at time T1. g. ΔT is set to 0.
h. The next key AOI is at time T1 + 10 seconds. i.
This means a total of 18 frames were captured from T1 to T1 + 10 seconds. j.
The server returns a sequence of 18 maps images for this section of the track.
k.
Options: Additional information required to define each bounding box vertex. This is vendor specific and may be used for supporting description of parameters required for
curve-based rendering of intermediate AOI maps. For instance, a spline curve based interpolation method may need additional “knobs” when treating each bounding box
vertex as a control point.
23.3.2 Rendering a Track
Rendering of frames is based on the Key Frame Animation technique that has been the basis of moving characters since the advent of traditional and computer animation.
2
Key AOI Entry: A Key AOI entry is analogous to a Key Frame in Key Frame Animation.
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80 A path has multiple key areas of interest bounding boxes where each AOI bounding box is a set
of four points. As we move forward or backward in time, the server is interpolating each point between consecutive key AOIs using a pre-defined interpolation method. The result is an
intermediate AOI at a given instant in time between the two key AOIs. From a server’s perspective, an intermediate frame is one GetMap request asking for one AOI.
Figure 12: Example path based AOI rendering of WAMI data
23.4 GetMap in WMS and Image Service
